[NativeNewYorker]

If zoning/landmarking is altered to allow more dense housing near existing transit, this is quite doable.

As the article notes, teeming Manhattan, already the US county with the greatest population density, now has 25% FEWER residents than it did early in the last century.

[HostileTerritory]

I have a friend who has a fairly small studio in Soho. The "living room" is reasonably large, but the sleeping area is an alcove with a mattress on the floor with a view of an airshaft, and the toilet and shower are in the kitchen which doubles as the foyer. Pretty shocking to anyone who has never lived in New York.

He lives there alone. In the 1870s, his studio would have been three separate tenement apartments, each one with multiple adults living there. Scary.

[Clemenza]

Remember that most of the growth will be in Queens, the Bronx, and even Staten Island. Manhattan and northern Brooklyn are largely inhabited by the childless, with the exception of some rather wealthy people. A century ago, much of the island was inhabited by the working class, which is why you see so many Catholic Churches, many of which are now practically empty on a Sunday.

If you look at the areas where population growth has been the strongest, they are places like Jackson Heights, Flushing, Sunset Park/Bay Ridge, University Heights, Norwood, and Staten Island's North Shore. The reason is immigration.